1. Field of the Invention
The invention relates to printing and dyeing wastewater treatment and more particularly to a printing and dyeing wastewater treatment and reuse apparatus and method therefore based on nanocatalysis and membrane electrolysis technology.
2. Description of Related Art
Textile industry typically includes five major fields such as textile, printing and dyeing, chemical fiber, garment and textile equipment manufacturing. With the rapid development of science and technologies, printing and dyeing industry has entered a period of rapid development, equipment and technology has improved significantly, constantly upgraded production technology and equipment, and printing and dyeing enterprises developed rapidly. So far there are more than 2000 printing and dyeing enterprises in China solely. Dyeing process is the production process of the various types of textile materials, fibers, yarns, and fabrics for physical and chemical treatment and it includes the pre-treatment of textile materials, dyeing, printing and finishing processes which are referred as printing processes. At present, the development of textile technology of producing eco-textiles and green manufacturing technology for guidance, from the process, additives, equipment and other multi-channel is proceeded well to seize resources and focus on every aspect of the production process of ecological problems. Further, efforts are made to optimize textile technology and reduce chemicals, water and energy consumption in order to achieve efficient, high-speed, environment protection purposes. Great efforts have been made at home and abroad to develop environmentally friendly dye additives, new technologies of water-saving, energy-saving, and discharge reduction, new equipment, less water consumption in dry dyeing, coatings, textile printing and dyeing as well as energy, water and other novel aspects of great development. While the textile industry, water and wastewater treatment technologies have seen rapid development, wastewater produced by textile printing and dyeing industry in China is still one of the key sources of pollution in industrial sectors according to the State Environmental Protection Administration statistics. Regarding printing and dyeing industry, printing and dyeing wastewater discharge volume of industrial sectors in the country is about fifth of total discharge. An important characteristic of dyeing wastewater as environmental pollution is its large volume. Currently, the world's annual production is about 80 to 90 dyeing tons and the annual production is 150,000 tons in China the highest in the world. In the production about 10% to 15% of dyeing materials used in printing are, together with wastewater, discharged into the environment. As China's textile industry and dyeing industry developed, printing and dyeing wastewater pollution of the environment is more serious. In 2004 industry-wide discharge is 1.36 billion cubic meters, while the total discharge of pollutants as COD (chemical oxygen demand) is numbered sixth of pollutants among various industrial sectors. Secondary, as an environmental pollutant, printing types are various and complicated. Worldwide, there are more than 30,000 kinds of synthetic dyeing and printing and dyeing having more than 80% of azobenzene bond, poly-aromatic ring complex organic compounds. Printing and dyeing industry is a chemical industry that is an extremely serious environmental pollution industry. Color of printing and dyeing wastewater is significant. Organics thereof are at high concentrations with complex components. It has multi-biodegradable substances and contains a large amount of inorganic salts, sulfides, etc. And industrial wastewater it produced is the most serious. Because printing of complex aromatic molecules with molecular structure is more difficult of removal, the structure in the design and manufacture phase is a stable oxidant in order to accommodate water or light conditions. Thirdly, it is the most refractory organics for hazardous dyeing, chemical stability, carcinogenic, teratogenic and mutagenic ‘three-induced’ effect. Remnants of dyeing wastewater components even in small concentrations, are discharged into water and can slow water flow, resulting in the destruction of aquatic ecosystems. Therefore, an effective dyeing wastewater treatment has become an important issue.
Printing and dyeing wastewater with high concentration of pollutants which is various and may contain toxic ingredients and have a high color characteristic. Currently, at home and abroad, wastewater treatment methods used are physical, chemical, biological, and other processing technologies as detailed below.
1. Physical Methods
It includes adsorption flotation, membrane separation, gas ultrasonic vibration method, distillation and other methods. The physical treatment method is the most widely used one. Currently, the activated carbon adsorption as used abroad, the law on the removal of dissolved organic matter in water is very effective, but it cannot remove the water and the hydrophobic colloidal dyeing of cationic dyeing, direct printing and dyeing, acid dyeing, printing and dyeing with reactive dyeing and other water-soluble than good adsorption properties. Adsorption flotation method is first used on some highly dispersed powdery inorganic adsorbent such as bentonite, kaolin, etc. in the printing to adsorb ions and other soluble substances, then adding flotation agent to be converted to hydrophobic particles removed by flotation. The acidic dyeing, printing and direct printing and dyeing have removal efficiency of 92%.
The membrane used in dyeing wastewater treatment technologies includes ultra-filtration and reverse osmosis. Ultrafiltration technology for treatment of dyeing wastewater contains dispersed decolorization rate 80% to 97% and TOC removal rate is 60% to 85%. RO dissolved solids removal rate is from 85% to 99%, and the average recovery of 75% dye to 85%.
It is possible of controlling the ultrasonic frequency and saturated gas. The ultrasonic technology has become an effective method for wastewater treatment. Zhangjiagang City Fine Chemical Plant in Kyushu, based on ultrasonic vibration technology and the wastewater treatment equipment FBZ, processes dyeing wastewater and obtains a color removal rate of 97%, CODCr removal rate of 90.6%, and a total pollution load reduction rate of 85.9%.
Chemical Method
Chemical methods include chemical coagulation, chemical oxidation, photochemical oxidation, electrochemical method and other methods. Chemical coagulation is a common method of dyeing wastewater treatment and was considered to be the most effective and economical bleaching technologies. Chemical oxidation dyeing wastewater decolorization is one of the main methods to use a variety of means for oxidation dyeing chromophore destruction bleaching. Oxidation by oxidants among other different conditions can be divided into chemical oxidation by ozone oxidation, and deep oxidation. In addition, the photochemical degradation of catalytic oxidation of organic matter as a deep oxidation technology has developed rapidly in recent years. Zhang Guilan (Zhang Guilan, dye wastewater in an open rotating photo-catalytic degradation of the pool, Textile Research, 2005, 263: 109-111) used this method to obtain a good degradation of dyeing wastewater decolorization. Electrochemical method is through the electrode reactions for dyeing wastewater purification. Micro-electrolysis method is the use of iron-carbon filler corrosion in the electrolyte solution of the original formation of numerous tiny batteries electrochemical wastewater treatment technology which is a set of electrolysis, coagulation, flocculation electricity, adsorption, and other physical and chemical effects in one method of treating wastewater. In the process of printing and dyeing wastewater treatment, dyeing molecules are adsorbed to the carbon surface first, and then at the electrodes oxidation or reduction reactions are occurred. Electrolysis electrode can also be used. Jin-Ping Jia, etc. (Jin-Ping Jia, etc., containing dye wastewater treatment methods Status and Progress, 2000, 191: 26-29) use activated carbon fibers as electrode conductivity of the electrode, adsorption, catalysis, redox (reduction-oxidation) actions, and flotation, comprehensive techniques to achieve adsorption-electrode reaction-desorption train flocculation process. The decolorization rate was 98%, and CODCr removal efficiency is greater than 80%. Yan Bin (Yan Bin, micro electrolysis dyeing wastewater applied research, Xiamen Institute of Technology, 2008, 16 (1): 18-22) studied the iron-carbon micro-electrode electrolysis technology blends of cotton and chemical fiber series woven fabrics produced decolorization and CODCr removal results in the iron-carbon mass ratio 2:1, HRT is 1.5 h time, COD removal efficiency up to 55%, color removal was 95%, BOD (biochemical oxygen demand)/COD from 0 3 to about 0.5. Luo Jing hygiene (Luo Jing hygiene, water treatment technology, 2005, 31 (11):67-70) used cyclic iron-carbon micro electrolysis containing dyes, dye intermediates, and additives such as wastewater study, the results show that the raw water pH has a great impact on the treatment effect. When the pH is 1 to 5:00, pH is lower, and its effect is better. When the pH is 1, COD removal rate is about 60% and more than 94% color is removed. Deng Sihong (Deng Sihong, Environmental Science and Management, 2008, 33 (3): 120-122) obtained results include high levels of pollutants, the concentration of large fluctuations, alkaline, high color, difficult biochemical dyeing wastewater using micro-electrolysis plus physicochemical and biological treatment. The process runs three consecutive months and the results indicate that the process is stable, less investment, low processing cost (per ton cost of treatment is about 0.765 RMB), COD, BOD, SS and color removal rates were 94%, 96%, 89%, and 96% respectively and water quality indicators meet discharge standards. Epolito William J, HanbaeYang, et al. use micro-electrolysis method to study RB4 (Reactive Blue4) wastewater. Experiment results showed that the decolorization rate increases as the pH and stirring intensity, the experiment temperature and ionic strength increases. Many other treatments of dyeing wastewater employing electrochemical method reported similar results.
3. Biochemical Method
Dyeing Wastewater has a poor biodegradability. If you use biochemical treatment, you can improve the activated sludge biological sludge activity MLSS and improve the performance. Alternatively, you can select efficient strains to improve the biochemical results. Breeding and training excellent bleaching flora is an important biochemical development direction. Other countries have carried out using mutation breeding, protoplast fusion, genetic engineering and other technologies for the formation of high-performance printing with multiple plasmids bleaching in engineering bacteria research. Recent studies show that the Pseudomonas bacteria, natans, Arthrobacter, Bacillus subtilis, yeast and other advantages of the oxidation dyeing degradation bacteria have considerable effects.
In recent years, the combination of chemical and physical methods for dyeing wastewater treatment and biological methods for dyeing wastewater treatment and physical methods developed rapidly. China Patent Number ZL200710008643.0 discloses a membrane-based technique of dyeing wastewater treatment method which is the chemical flocculation and precipitate, biological treatment and reverse osmosis separation technology combining printing and dyeing wastewater treatment. While above methods have better treatment effect, they have the following problems:
In physical fields, activated carbon adsorption, while having good effect, but the activated carbon regeneration is difficult, has a high cost, and its application is limited. Many enterprises are turning to other inexpensive, readily available materials adsorbents. Although electrolysis, oxidation of dyeing wastewater in the removal of color have a certain effect, but often have unsatisfactory COD removal, treatment chemicals cost is relatively high, and many new oxidation methods are still in the experimental study stage without being industrialized.
In biochemical fields, printing and dyeing typically is fine chemical products, with a small quantity and variety of features, its complex structure, long production process, from raw materials to finished products are often accompanied by nitration, condensation, reduction, oxidation, diazotization, coupling, etc. Unit operations, products and more product yield is low, wasted organic complex composition, printing and dyeing production of chemical reactions and separation, purification, washing and other process operations are using water as a solvent with a large volume of water. Biological treatment of dyeing wastewater although has advantage of less investment, but there are still difficult of being applied to microorganisms dyeing wastewater treatment and has water quality fluctuations, toxicity and other shortcomings. There is a sludge treatment, anaerobic biogas processing and management of complex issues. In addition, although the use of iron-carbon as electrode electrolysis method, dyeing wastewater has made some progress, but it brings a lot of precipitated iron-carbon consumption, so that the treated wastewater is difficult to use and only meet general discharge standards.
Dyeing wastewater treatment using a single treatment is often difficult to achieve desired effects. Conventional approach is to combine the treatment methods and unfortunately it is a long process, running costs are high, the water quality is poor and has other defects. The treated wastewater only reaches stage II discharge standards. Because of this wastewater has gone through the biochemical, chemical, physico-chemical and other methods of treatment, physical and chemical properties are very stable, very difficult to purify subsequent bleaching, the typical methods are difficult to carry out further bleaching purification, and this reaches stage II discharge standard about advanced treatment of wastewater. Discharge on the environment will also cause long-term effects. On the other hand, the current freshwater resources are increasingly polluted. Water conflicts have become increasingly prominent, such as dyeing wastewater being treated for reuse. It not only significantly reduces the impact on the environment but also saves a lot of freshwater resources.